Optimization of Food Waste and Biochar In-Vessel Co-Composting

Chaher, Nour El Houda; Chakchouk, Mehrez; Engler, Nils; Nassour, Abdallah; Nelles, Michael; Hamdi, Moktar

doi:10.3390/su12041356

Cited by 29 publications

(25 citation statements)

References 54 publications

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“…These were corrected at a later stage and regulated in the range of 20-30 for different feedstocks by the addition of CM for anaerobic digestion and GW for thee composting process as co-substrates [61]. As the presence of minor elements is crucial for the microorganism communities, some micro-and macro-elements were identified [62]. Copper (Cu), nickel (Ni), and zinc (Zn) were detected in varying quantities, with Zn recording the highest quantities in the different substrates.…”

Section: Characterization Of the Selected Biowastementioning

confidence: 99%

Potential of Sustainable Concept for Handling Organic Waste in Tunisia

et al. 2020

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Nowadays, Tunisia is seeking to implement cost-efficient and sustainable solutions in relation to the treatment of organic waste which, at up to 65%, makes up the largest proportion of total waste generated in the country. Therefore, an efficient tool for decision makers is needed to provide a clear approach about the potential of organic waste as well as the treatment concept, which can be adapted based on technical requirements and local conditions. Results revealed that there is a high variation in terms of the nature of the collected biowaste, which affects the selection of the adopted bioprocess for each geographical zone of the study area. Three main categories of biowaste are produced along the coastline of Tunisia: food waste (FW) (102.543 t/a); green waste (GW) (1.326.930 t/a); and cattle manure (CM) (1.548.350 t/a). Based on the results of similar projects and laboratory-scale research work, anaerobic and aerobic digestion were examined. Regarding aerobic digestion, the monitoring of several physicochemical parameters ascertained that the co-composting of FW and GW at different ratios (GW: FW = 100:0, 75:25, 50:50, and 25:75) allowed the production of a stable and mature compost. A highly qualified end-product was generated from each trial categorized as a finished compost of class V with reference to German Standards of compost. Regarding the anaerobic process, different feedstock mixtures (FW:CM = 0:1, 1:1, 2:1, and 3:1) were prepared to feed semi-continuous anaerobic reactors. However, a significant improvement in the process development was recorded for digesters including a higher fraction of FW, which produced 0.846 LN/kg VSin as the maximum biogas production. Therefore, biological treatments of food waste and different co-substrates seems to be a suitable technique for Tunisia in terms of waste management, environmental, and energy aspects. However, the evaluation of the efficiency of the proposed biological treatments was also verified by a draw-up of a technical and economic feasibility analysis. Although the cost–benefit estimations proved that the profits from both the compost and biogas plants would be very modest, the feasibility of such sustainable projects should not only be evaluated on an economic basis, but also by taking into account socio-environmental considerations including decreasing environmental threats, providing work opportunities, increasing incomes, stimulating public awareness as well as reducing the operating costs linked to landfilling.

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Section: Characterization Of the Selected Biowastementioning

confidence: 99%

Potential of Sustainable Concept for Handling Organic Waste in Tunisia

et al. 2020

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“…As the ratio between NH 4 + and NO 3 − ; the nitri cation index (NI) is considered as an indicator of the compost's stability (Chaher et al, 2020a), it was monitored during the composting process to evaluate the nitrogen transformation reactions. Figure 6 showed that, during the thermophilic phase, NI of the unamended reactor (A1) was considerably higher than the amended one (A2 Accomplishing the cooling phase, NI for both of A1 and A2 was progressively dropping to reach approximatively 3 at the end of the process.…”

Section: Nitri Cation Index (Ni) and Respiration Activity (At4)mentioning

confidence: 99%

“…Indeed, the signi cant amounts of metal components which marked A2 were predicted by the initial rate of HMs provided by the digestate as described in Table 1. However, despite the remarkable content in terms of HMs, A2 met all the laws applicable in several countries and it was classi ed as a Class B biofertilizer in reference to the German Standards (Chaher et al, 2020a). Additionally, Table 4 shows that the compost gathered from A1 was categorized as Class A based on the German limits and illustrated that both amended and unamended reactors generated high quali ed end products.…”

Section: Effect Of Digestate Addition On End-product Qualitymentioning

confidence: 99%

“…However, the opportunity to use the different types of organic waste as compost requires scienti c studies that endorse it to guide users concerning the aspects behind the better management of the composting operation. In conjunction with the quantitative and life cycle-based evaluations, a comprehensive technical-scienti c view of bio-waste composting should also include increasing the currently limited knowledge of the process performance in terms of monitoring and controlling the crucial factors affecting the e ciency of the composting units (Asadu et al, 2019;Chaher et al, 2020a). In this context, Moisture content (MC) is a critical factor in the composting process.…”

Section: Introductionmentioning

confidence: 99%

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From Anaerobic to Aerobic Treatment: Upcycling of Digestate as a Moisturizing Agent for in-vessel Composting Process

Chaher

Hemidat

Chakchouk

et al. 2020

Preprint

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In Tunisia, there are crucial challenges facing both urban and rural areas, the most prominent of which are the production of organic waste, the need for waste treatment, the demand for water and energy and the need for a circular economy. To this end, the study was designed to develop a technical concept on closed cycle ‘biowaste to bioenergy’ treating, basically food waste (FW) through combined biological processes. In this approach, the generated digestate from FW anaerobic reactors was used successfully as a moisturizing agent for FW in vessel-composting. Four types of digestate were examined to be used as moisturizing agent (MA). The selection of the appropriate MA was achieved based on technical criteria ; moisture content (MC), C : N ratio and heavy metals concentrations. The findings showed that the digestate obtained from anaerobic co-digestion of food waste and wheat straw (D1) was the most efficient AD-effluent to be added. In terms of composting process performance, the thermophilic phase of the amended reactor (A1) lasted 16 days and reached higher temperatures of about 72°C, while the unamended one (A1) was characterized by a thermophilic temperature of around 66°C indicating that the end-products were of a pathogen-free compost. When it comes to the physico-chemical factors examined demonstrating that the biological conditions were sufficiently developed. The findings showed overall decreasing profiles during the composting period for moisture, C : N ratio as well as nitrification index (NI). From the quality-point of view, it was found that heavy metal concentrations had lower limits than those values set by German standards. Moreover, all the compost samples appeared to be stable and classified as class IV and V end-product.

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“…Therefore, by comparing temperature trends, the modi ed reactor speeded up the thermophilic phase and expanded its duration (15 days) which emphasised the effectiveness of digestate addition. It might be also due to the in uence the introduction of biochar to anaerobic reactors which played a crucial role to enhance the AD residue properties by intensifying the microbial activity (Chaher et al 2020a and Suthar 2020). However, assuming that the digestion acquired from AD reactors can be used directly as a soil conditioner, it was clear that pasteurization is mandatory to ensure its puri cation, which is the largest energy consumer in the anaerobic digestion (AD) chain (Liu et al, 2019).…”

Section: Physio-chemical Properties Of the Raw Materialsmentioning

confidence: 99%

Upgrading of Food Waste in-vessel Composting Process: Effects of Biochar-rich Digestate Addition

Chaher¹,

Nassour²,

Nelles³

et al. 2020

Preprint

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Nowadays, Tunisia faces challenging environmental and energic issues which concern mainly the implementation of an appropriate solid waste management system dealing with the high production of biowaste in one hand and the increased need for water and energy resources in the other hand. Therefore, the current study intended to develop a technical concept on closed cycle ‘biowaste to bioenergy’, treating mainly food waste (FW) through combined biological processes. In this approach, FW anaerobic digestion (AD) residue was destined to feed FW in vessel-composting as a valuable input material. To this end, the produced digestates from amended and unamended anaerobic reactors were entirely examined to select later the most appropriate AD-effluent. Therefore, the identification of the convenient digestate was achieved based on technical criteria ; moisture content (MC), C : N ratio and heavy metals concentrations. The findings showed that the digestate obtained from different digesters was characterized by a high moisture content which inspired its utilization as an unconventional moisturizing agent (MA) reducing the fresh water consumption during the composting process. Because of the high C : N ratio, relatively significant rate of the needed macro and micro-nutrients, the exploitation of biochar-rich digestate was recomended to be used as an unconventional MA in one hand and an aerobic co-substrate booster in the other hand. Results showed that D3 addition promoted the composting process performance comparing to the blank test (A1). Indeed, the thermophilic phase of the amended reactor (A2) lasted 15 days and reached higher temperatures of about 67 °C, while the unamended one (A1) was characterized by a thermophilic temperature of around 63 °C indicating that the end-products were of a pathogen-free compost. When it comes to the physico-chemical factors examined demonstrating that the biological conditions were sufficiently developed. The findings showed overall decreasing profiles during the composting period for moisture, C : N ratio as well as nitrification index (NI). From the quality-point of view, it was found that heavy metal concentrations had lower limits than those values set by German standards. Moreover, all the compost samples appeared to be stable and classified as class IV and V end-product.

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Optimization of Food Waste and Biochar In-Vessel Co-Composting

Cited by 29 publications

References 54 publications

Potential of Sustainable Concept for Handling Organic Waste in Tunisia

Potential of Sustainable Concept for Handling Organic Waste in Tunisia

From Anaerobic to Aerobic Treatment: Upcycling of Digestate as a Moisturizing Agent for in-vessel Composting Process

Upgrading of Food Waste in-vessel Composting Process: Effects of Biochar-rich Digestate Addition

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